Delay ShutdownChannelIfExistsAsync until cold start

[kshyju]

Investigate whether we can delay the code to shutdown the unused channels so that they don't impact cold start.

if (_workerRuntime != null && rpcWorkerChannel != null)
{
    bool envReloadRequestResultSuccessful = false;
    if (UsePlaceholderChannel(rpcWorkerChannel))
    {
        _logger.LogDebug("Loading environment variables for runtime: {runtime}", _workerRuntime);
        envReloadRequestResultSuccessful = await rpcWorkerChannel.SendFunctionEnvironmentReloadRequest();
    }

    if (envReloadRequestResultSuccessful == false)
    {
        _logger.LogDebug("Shutting down placeholder worker. Worker is not compatible for runtime: {runtime}", _workerRuntime);
        // If we need to allow file edits, we should shutdown the webhost channel on specialization.
        await ShutdownChannelIfExistsAsync(_workerRuntime, rpcWorkerChannel.Id);
    }
}
_shutdownStandbyWorkerChannels();

The line await ShutdownChannelIfExistsAsync(_workerRuntime, rpcWorkerChannel.Id); - Should that be wrapped inside the "delay until cold start" utility ?

Comment from @safihamid on #9602

do we need to shutdown the channel immediately or can wait like 5 sec? trying to see if this will have negative cold start impact on existing apps once we switch to opt out only